Photomechanical process



Patented June 3, 1924.

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Free.

ANNA SCHWARZ, GEB. HOPPEHEL, OF BERLIN, GERMANY, ASSIGNOR TO AUGUST CARL LENTZ, O'F IRON RIDGE, VIISCONSIN.

PHOTOMECHANICAL rnoonss.

No Drawing.

To alhvhom it may concern:

Be it known that I, ANNA SGHWARZ, geb. HOPPEHEL, a citizen of Germany, and a resident of Berlin, Prussia, Germany, have invented new and useful Improvements in Photomechanical Process, of which the following is a full, clear, and exact specification.

. My invention relates to photo-mechanical 1 processes and refers particularly to the production of zinc printing plates.

The present employed methods of pr0ducing zinc printing plates through the medium of bichromate emulsions, with or without the employment of transfer prints present numerous difficulties and produce plates so far removed from desirable attributes, that their application has been largely replaced by other photo-mechanical methods.

The use of bichromate emulsions upon grained, or rough, zinc plates has in particular many disadvantages, among which is the liability of the bichromate film to break and to become sharp and pointed, thus producing irregular and unsatisfactory printed results.

I have found that these undesirable results are due to the fact that the usually employed albumen, or gelatin, bichromate emulsions do not sufficiently penetrate theinterstices of the rough plate and hence are easily detached therefrom by the further operations, or by the printing processes.

I have found that this objectionable feature may be overcome by employing acetic acid, or lactic acid, in the developing bath, particularly when gum arabic is used in the emulsion.

This valuable attribute can be further enhanced if benzine be added to the color ink and if a soft resin, such as elemi, or copal be employed.

As an example of one method of applying my process, I give the foll0wing:-

The carefully cleaned and dried Zinc plate is evenly and thoroughly covered with an emulsion consisting of 1 part best gum arabic dissolved in 3.5 parts water together with 10 parts ammoniumv bichromate dissolved in a small quantity of warm water. If desired, 10 parts alum may be added. The plate is then quickly dried and retained in a semi-dark room.

The plate is exposed under a positive in any suitable manner, the time of exposure Application filed June 13, 1923. Serial No. 645,198.

depending upon the intensity of the light and the depth of thepositive.

The plate is now uniformly and completely treated with a developer consisting of 900 parts chemically pure glycerine, 50 parts water and 50 parts acetic acid, or lactic acid, which is thoroughly rubbed into the emulsion by means of a felt, or plush, cushion.

hen the impression, or print, appears distinctly, the superfluous developer is removed by means of a rubber squeegee.

The color tincture composed of 900 c. c. denatured alcohol, 50 grams elemi, or copal, 27 grams shellac and 3 c. c. benzine, is then rubbed over the plate by means of a cloth and and the fatty ink is then applied to the plate by means of a cloth until the impression appears in full black line. places are immediately recognizable and can be remedied by intensive rubbing or additional developing.

Should the plate become too dry, developer must be again applied so that the emulsion is again saturated.

The plate is then placed in hydrochloric acid 1:25 which causes the bichromate film to dissolve.

The plate is now cleaned, etched in the usual manner and made ready for printing.

The lines on the plate thus produced are clear, clean, prominent and permanent.

By bichromate emulsions in my specification and claims I mean emulsions of bichromate and gum arabic. with or without, the addition of alum and by organic de- Defective veloping acids I mean acetic acid and lactic emulsion, developing with a developer containing an organic developer acid, treating with a color tincture and a fatty ink, treating with hydrochloric acid and acid etching the resulting plate.

3. The process of producing zinc etched reproductions which comprises treating the zinc plate with a gum-arabic-bichromate emulsion, developing with a developer containing an organic developer acid and glycerine treating with acolor tincture and fatty ink, treating with hydrochloric acid and acid etching the resulting plate.

at. The process of producing zinc etched reproductions which comprises treating the zinc plate with a gum-arabic-bichromate emulsion, developing with a developer containing lactic acid, treating with a mixture containing elemi and a fatty ink, treating with hydrochloric acid and acid etching the resulting plate.

5. The process of producing zinc etched reproductions which comprises treating the zinc plate with a gumarahic-bichromate emulsion, developing with a developer conzinc plate with a gum-a1abicbichromate emulsion, developing with'a developer containing an organic developer acid and glycerine, treating with a mixture containing a soft resin and a fatty ink, treating with hydrochloric acid and acid etching the resulting plate.

7. The process of producing zinc etched reproductions which comprises treating the zinc plate with a gum-arabiobichroma'te emulsion, developing with a developer containing an organic developer acid, treating with a mixture containing alcohol, benzine, shellac, aresin and a fatty ink, treating with hydrochloric acid and'acid etching the resulting plate.

8. The process of producing zinc etched reproductions which comprises treating the zinc plate with a gum-arabic-bichromate emulsion, developing with a developer containing an organic developer acid-andglycerine, treating with a mixture containing alcohol, benzine, shellac, a resin and a fatty ink, treating with hydrochloric acid and acid etching the resulting plate.

Signedat Berlin, Germany, this 25th day oi lWay, 19 23.

ANNA SCHWARZ, geb. HOPPEHEL. 

